Gilly,
true it looks a bit different in 112/113s, but you are correct anyways, it's all in one. How they do the level measurement? Remember it uses two capacitors and one gets the dielectric constant, between the quality and common electrode. Then it reads the capacitance of the second, between level and common electrodes and since the capacitance depends on the dielectric of the medium, oil or air in this case, one can calculate the fraction of the level electrode covered by oil and thus obtain the level.
Delphi also developed an oil level meter, about 2 years later, and put a nice writeup on the net, including a graph showing level readings of 5 different oils (Figure 2).
http://www.delphi.com/pdf/techpapers/2000-01-1366.pdf
PS. The temperature sensor in the QLT is a PT1000 from Heraeus GmbH (the best, very precise) as far as I know.
Enjoy,
Wolfgang